I would like to ask here if there is a good means to get an overview
where the btrfs file system usage actually comes.
In our case, /var/lib/docker with various docker images appears to be
the culprit, but even there, it seems to be hard to get a realistic
usage information: "du -ksh /var/lib/docker" is reporting far too much
(I think because of the btrfs layering employed by docker), and
"docker images" not enough to justify the usage.
A think a good idea might be relocating /var/lib/docker to a separate
partition out of scope of the btrfs default filesystem?